The long-term goals of this research project are to elucidate the molecular and cellular mechanisms for neuroadaptations to ethanol. Previous studies have identified two new Drosophila mutants with a heightened sensitivity and impaired tolerance to ethanol. Preliminary spatial expression studies of one mutant, named homer, have suggested that the normal gene's function is sufficient in GABAergic neurons that innervate the ellipsoid body for normal behavioral responses to ethanol. These studies will be confirmed and extended. In addition, the directed expression of RNAi constructs and dominant negatives will be used to define where Corner expression is required in the adult brain for wild type behavioral responses to ethanol. Newly developed techniques that provide for experimenter control over transgene expression in time and space will be used to ascertain whether homer is required during development or whether it is required physiologically in the adult fly. Similar time and space expression studies using a normal transgene of the second mutant, named yps, will be performed to ascertain whether this gene's function is required in the same set of neurons and at the same time as homer for normal ethanol responses. RNA from neurons that require homer and/or yps will be isolated using newly developed affinity techniques and used to probe microarrays to define the changes in gene expression that occur with ethanol exposure in this specific set of neurons. The observed changes in gene expression with ethanol exposure will be used to predict which genes are functionally involved in behavioral responses to ethanol, and mutants in these genes will be assayed to further define the molecular genetic requirements for normal ethanol sensitivity and tolerance. These studies will further our understanding of the genetic basis for ethanol sensitivity and tolerance, important parameters for susceptibility to alcoholism.